Prioritizing input and compositor tasks in the blink scheduler.

Source/platform/scheduler/Scheduler.h

Index: Source/platform/scheduler/Scheduler.h
diff --git a/Source/platform/scheduler/Scheduler.h b/Source/platform/scheduler/Scheduler.h
index c492e580aa17268afe30b6c439a9c08acd08638f..1fb0445baee87426a6545b0f254f4964af18c58a 100644
--- a/Source/platform/scheduler/Scheduler.h
+++ b/Source/platform/scheduler/Scheduler.h
@@ -6,8 +6,12 @@
 #define Scheduler_h
 
 #include "platform/PlatformExport.h"
+#include "platform/TraceLocation.h"
+#include "public/platform/WebThread.h"
+#include "wtf/Deque.h"
 #include "wtf/Functional.h"
 #include "wtf/Noncopyable.h"
+#include "wtf/ThreadingPrimitives.h"
 
 namespace blink {
 class WebThread;
@@ -49,20 +53,66 @@ public:
     void setSharedTimerFireInterval(double);
     void stopSharedTimer();
 
+    void runPendingTasks();

[Sami, 2014/08/07 14:24:45]

This one doesn't need to be public, does it?

+
 private:
     Scheduler();
     ~Scheduler();
 
-    void scheduleTask(const TraceLocation&, const Task&);
     void scheduleIdleTask(const IdleTask&);
 
     static void sharedTimerAdapter();
     void tickSharedTimer();
 
     static Scheduler* s_sharedScheduler;
-    blink::WebThread* m_mainThread;
 
+    class TracedTask {
+    public:
+        TracedTask(Task task, TraceLocation location)

[Sami, 2014/08/07 14:24:45]

const Task& and const TraceLocation&

[alexclarke, 2014/08/07 15:15:29]

Done.

+            : m_task(task)
+            , m_location(location) { }
+
+        void run();
+
+    private:
+        Task m_task;
+        TraceLocation m_location;
+    };
+
+    class LockingTracedTaskDeque {
+    public:
+        void append(const TracedTask& value)
+        {
+            Locker<Mutex> lock(m_mutex);
+            m_queue.append(value);
+        }
+
+        bool isEmpty()

[Sami, 2014/08/07 14:24:45]

Could we somehow combine isEmpty() and takeFirst() so that we only take the lock
once?

[alexclarke, 2014/08/07 15:15:29]

Done.

+        {
+            Locker<Mutex> lock(m_mutex);
+            return m_queue.isEmpty();
+        }
+
+        TracedTask takeFirst()
+        {
+            Locker<Mutex> lock(m_mutex);
+            return m_queue.takeFirst();
+        }
+
+    private:
+        WTF::Deque<TracedTask> m_queue;
+        Mutex m_mutex;
+    };
+
+    // These members can be accessed from any thread.
+    blink::WebThread* m_mainThread;
+    LockingTracedTaskDeque m_pendingInputTasks;
+    LockingTracedTaskDeque m_pendingCompositorTasks;
+    LockingTracedTaskDeque m_pendingLowPriorityTasks;
     void (*m_sharedTimerFunction)();

[Sami, 2014/08/07 14:24:45]

This member should only be used on the main thread, right?

+
+    void maybePostTaskLoopOnMainThread();

[Sami, 2014/08/07 14:24:45]

Could you move these two before the data member declarations?

+    void runHighPriorityTasks();
 };
 
 } // namespace blink